Assay systems capable of detecting the presence or absence of antibodies generated in response to the presence of viral antigens are well known. Such assay systems have proved useful in, inter alia, the diagnosis of various disease and infectious states, for example, acquired immune deficiency syndrome (AIDS), AIDS related complexes (ARC or pre-AIDS), T-lymphocytic leukemia, and T-lymphocytic lymphoma.
The known assay systems, which employ antibody-antigen binding, ordinarily are designed to detect solely the presence or absence of IgG (immunoglobulin G). The appearance of detectable IgG directed to antigens in an infected/immunized individual, in many instances, does not occur until 30-40 days after initial infection. Typically, the IgG class antibodies are often present for months or years after infection or immunization with a foreign agent, such as a virus.
The presence of circulating IgG directed to an immunizing antigen during the course of infection or immunization is preceded by the presence of circulating IgM (immunoglobulin M) antibody directed against the antigen/immunogen. IgM antibody is often present as early as 14 days, possibly earlier, after infection/immunization. Unlike IgG antibody which remains for months or years after infection, IgM antibody loses titer 30-35 days after initial infection.
It is widely recognized that diagnostics which can detect antibodies other than IgG are desirable. For example, it is known that generally after confrontation with a foreign agent, the human immune system responds by generating antibodies against the foreign agent or antigen. It is believed, as previously discussed, that IgM, not IgG, is produced first. IgM is, however, a relatively short-lived antibody. While it may be produced shortly after infection, IgM specific antibodies fall, eventually below detectable levels, as IgG is produced in increasing amounts. Because IgM has a short life span, IgM specific antibodies are typically below detectable levels before many diseases can even be diagnosed using known diagnostic assay methods.
As can be appreciated, assays capable of detecting IgM will be useful in facilitating early detection of various infections and diseases. Early diagnosis facilitates treatment, and minimizes the risk of spreading infection.
The present invention overcomes the limitations associated with conventional assay techniques because it provides a Quick Western Blot assay for detecting the presence or absence of IgM class antibody alone or simultaneously with the detection of IgG.
Infections caused by the human retroviruses result in the appearance of antibodies in the serum, and other body fluids of the infected victim.
AIDS, which was first diagnosed in 1981, is known to be caused by a human retrovirus called HIV-1 (Human Immunodeficiency Virus-1). It has recently been reported that another human retrovirus, designated HIV-2 also causes AIDS.
The human retroviruses which are associated with AIDS are believed to be transmitted through intimate sexual contact as well as through blood.
Recently, investigators have become interested in two other human retroviruses, designated HTLV-I and HTLV-II. (HTLV means Human T-lymphotropic virus). Thus far, neither HTLV-I nor HTLV-II has been identified as the specific causative agent for any particular disease. These retroviruses, however, have been isolated from patients diagnosed with T-lymphocytic leukemia and lymphoma. Antibodies to HTLV-I have been also found in patients diagnosed with chronic, progressive spastic paraparesis (PSP) secondary to myelopathy. Neurology Alert, Vol. 6, no. 11, July 1988. It is presently believed that HTLV-I and HTLV-II are transmitted through blood. As more information about these retroviruses is revealed, it is predicted that as with HIV-1, all blood supplies will be screened for the presence of antibodies to HIV-2, HTLV-I and HTLV-II. Thus, as previously mentioned, it is advantageous to be able to detect the presence of IgM antibodies as well as IgG antibodies to facilitate early detection of infections and minimize the risk of spreading such infection.